Asp.Net change value of textbox in grid on selected Index changed

Question

I have this grid on which I am dynamically adding controls. Now I want to change the respective value of Cost Price and Sale Price on Products selected index changed event. The problem is I cannot get the specific row. Below the code I have done so far.

    <asp:GridView ID="grdSales" runat="server"
                    ShowFooter="True" AutoGenerateColumns="False"
                    CellPadding="4" CssClass="table table-hover table-striped"
                    GridLines="None" OnRowDeleting="grdSales_RowDeleting" OnRowCommand="grdSales_RowCommand">
                    <Columns>
                        <asp:BoundField DataField="RowNumber" HeaderText="SNo" />

                        <asp:TemplateField HeaderText="Products">
                            <ItemTemplate>
                                <asp:DropDownList ID="ddlProducts" runat="server"  CssClass="grid-control form-control" OnSelectedIndexChanged="ddlProducts_SelectedIndexChanged">
                                </asp:DropDownList>
                            </ItemTemplate>
                        </asp:TemplateField>


                        <asp:TemplateField HeaderText="Cost Price">
                            <ItemTemplate>
                                <asp:TextBox ID="txtCp" runat="server" CssClass="grid-control form-control"></asp:TextBox>
                            </ItemTemplate>
                        </asp:TemplateField>
                          <asp:TemplateField HeaderText="Sale Price">
                            <ItemTemplate>
                                <asp:TextBox ID="txtSp" runat="server" CssClass="grid-control form-control"></asp:TextBox>
                            </ItemTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="Total Units">
                            <ItemTemplate>
                                <asp:TextBox ID="txtUnits" runat="server" CssClass="grid-control form-control"></asp:TextBox>
                            </ItemTemplate>
                              <FooterStyle HorizontalAlign="Left" />
                            <FooterTemplate>
                               Total Journal Cost: <asp:Label ID="lblTotalCost" runat="server" Text="0"></asp:Label>
                            </FooterTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="Total Cost">
                            <ItemTemplate>
                                <asp:TextBox ID="txtTotal" runat="server" CssClass="grid-control form-control"></asp:TextBox>
                            </ItemTemplate>




                             <FooterStyle HorizontalAlign="Left" />
                            <FooterTemplate>
                                <asp:Button ID="ButtonAdd" runat="server" Text="Add New Row" CssClass="btn btn-primary" OnClick="ButtonAdd_Click" />
                            </FooterTemplate>
                        </asp:TemplateField>

                        <asp:CommandField
                            ShowDeleteButton="True" />
                    </Columns>


                </asp:GridView>

and my code behind is

 #region Private Functions
    private void FirstGridViewRow()
    {
        DataTable dt = new DataTable();
        DataRow dr = null;
        dt.Columns.Add(new DataColumn("RowNumber", typeof(string)));

        dt.Columns.Add(new DataColumn("Products", typeof(string)));

        dt.Columns.Add(new DataColumn("CostPrice", typeof(string)));
        dt.Columns.Add(new DataColumn("SalePrice", typeof(string)));
        dt.Columns.Add(new DataColumn("TotalUnits", typeof(string)));
        dt.Columns.Add(new DataColumn("TotalCost", typeof(string)));
        dr = dt.NewRow();

        dr["RowNumber"] = 1;

        dr["Products"] = string.Empty;

        dr["CostPrice"] = string.Empty;
        dr["SalePrice"] = string.Empty;
        dr["TotalUnits"] = string.Empty;
        dr["TotalCost"] = string.Empty;


        dt.Rows.Add(dr);

        ViewState["CurrentTable"] = dt;

        grdSales.DataSource = dt;
        grdSales.DataBind();
        AddNewRow();
        SetRowData();
        if (ViewState["CurrentTable"] != null)
        {
            DataTable dtOld = (DataTable)ViewState["CurrentTable"];
            DataRow drCurrentRow = null;
            int rowIndex = Convert.ToInt32(0);
            if (dtOld.Rows.Count > 1)
            {
                dtOld.Rows.Remove(dt.Rows[rowIndex]);
                drCurrentRow = dtOld.NewRow();
                ViewState["CurrentTable"] = dtOld;
                grdSales.DataSource = dtOld;
                grdSales.DataBind();

                for (int i = 0; i < grdSales.Rows.Count - 1; i++)
                {
                    grdSales.Rows[i].Cells[0].Text = Convert.ToString(i + 1);
                }
                SetPreviousData();
            }
        }

    }
    private void AddNewRow()
    {
        int rowIndex = 0;

        if (ViewState["CurrentTable"] != null)
        {
            DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
            DataRow drCurrentRow = null;
            if (dtCurrentTable.Rows.Count > 0)
            {
                for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
                {

                    DropDownList ddlProducts =
                      (DropDownList)grdSales.Rows[rowIndex].Cells[1].FindControl("ddlProducts");

                    TextBox txtCostPrice =
                      (TextBox)grdSales.Rows[rowIndex].Cells[2].FindControl("txtCp");
                    TextBox txtSalePrice =
                     (TextBox)grdSales.Rows[rowIndex].Cells[3].FindControl("txtSp");
                    TextBox txtUnits =
                     (TextBox)grdSales.Rows[rowIndex].Cells[4].FindControl("txtUnits");
                    TextBox txtTotal =
                     (TextBox)grdSales.Rows[rowIndex].Cells[5].FindControl("txtTotal");

                    drCurrentRow = dtCurrentTable.NewRow();
                    drCurrentRow["RowNumber"] = i + 1;


                    dtCurrentTable.Rows[i - 1]["Products"] = ddlProducts.SelectedValue;

                    dtCurrentTable.Rows[i - 1]["CostPrice"] = txtCostPrice.Text;
                    dtCurrentTable.Rows[i - 1]["SalePrice"] = txtSalePrice.Text;
                    dtCurrentTable.Rows[i - 1]["TotalUnits"] = txtUnits.Text;
                    dtCurrentTable.Rows[i - 1]["TotalCost"] = txtTotal.Text;


                    rowIndex++;
                }
                dtCurrentTable.Rows.Add(drCurrentRow);
                ViewState["CurrentTable"] = dtCurrentTable;

                grdSales.DataSource = dtCurrentTable;
                grdSales.DataBind();
            }
        }
        else
        {
            Response.Write("ViewState is null");
        }
        SetPreviousData();
    }
    private void SetPreviousData()
    {
        int rowIndex = 0;
        if (ViewState["CurrentTable"] != null)
        {
            DataTable dt = (DataTable)ViewState["CurrentTable"];
            if (dt.Rows.Count > 0)
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {

                    DropDownList ddlProducts =
                      (DropDownList)grdSales.Rows[rowIndex].Cells[1].FindControl("ddlProducts");

                    TextBox txtCostPrice = (TextBox)grdSales.Rows[rowIndex].Cells[2].FindControl("txtCp");
                    TextBox txtSalePrice = (TextBox)grdSales.Rows[rowIndex].Cells[3].FindControl("txtSp");
                    TextBox txtUnits = (TextBox)grdSales.Rows[rowIndex].Cells[4].FindControl("txtUnits");
                    TextBox txtTotal = (TextBox)grdSales.Rows[rowIndex].Cells[5].FindControl("txtTotal");


                    //Added these lines

                    ddlProducts.DataValueField = "Key";
                    ddlProducts.DataTextField = "Value";
                    ddlProducts.DataSource = BindProductsDdl();
                    ddlProducts.DataBind();

                    //****************

                    ddlProducts.SelectedValue = dt.Rows[i]["Products"].ToString();

                    txtCostPrice.Text = dt.Rows[i]["CostPrice"].ToString();
                    txtSalePrice.Text = dt.Rows[i]["SalePrice"].ToString();
                    txtUnits.Text = dt.Rows[i]["TotalUnits"].ToString();
                    txtTotal.Text = dt.Rows[i]["TotalCost"].ToString();
                    rowIndex++;
                }
            }
        }
    }
    private void SetRowData()
    {
        int rowIndex = 0;

        if (ViewState["CurrentTable"] != null)
        {
            DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
            DataRow drCurrentRow = null;
            if (dtCurrentTable.Rows.Count > 0)
            {
                for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
                {

                    DropDownList ddlProducts =
                       (DropDownList)grdSales.Rows[rowIndex].Cells[1].FindControl("ddlProducts");

                    TextBox txtCostPrice = (TextBox)grdSales.Rows[rowIndex].Cells[2].FindControl("txtCp");
                    TextBox txtSalePrice = (TextBox)grdSales.Rows[rowIndex].Cells[3].FindControl("txtSp");
                    TextBox txtUnits = (TextBox)grdSales.Rows[rowIndex].Cells[4].FindControl("txtUnits");
                    TextBox txtTotal = (TextBox)grdSales.Rows[rowIndex].Cells[5].FindControl("txtTotal");

                    drCurrentRow = dtCurrentTable.NewRow();

                    drCurrentRow["RowNumber"] = i + 1;

                    dtCurrentTable.Rows[i - 1]["Products"] = ddlProducts.Text;

                    dtCurrentTable.Rows[i - 1]["CostPrice"] = txtCostPrice.Text;
                    dtCurrentTable.Rows[i - 1]["SalePrice"] = txtSalePrice.Text;
                    dtCurrentTable.Rows[i - 1]["TotalUnits"] = txtUnits.Text;
                    dtCurrentTable.Rows[i - 1]["TotalCost"] = txtTotal.Text;

                    rowIndex++;
                }

                ViewState["CurrentTable"] = dtCurrentTable;
                //grvStudentDetails.DataSource = dtCurrentTable;
                //grvStudentDetails.DataBind();
            }
        }
        else
        {
            Response.Write("ViewState is null");
        }
        //SetPreviousData();
    }
    private void BindControls()
    {
        BindWarehouseDdl(); BindStaticLists();

    }

    private Dictionary<int, string> BindProductsDdl()
    {
        Dictionary<int, string> Get = new Dictionary<int, string>();
        for (int i = 0; i < Products.Count; i++)
        {
            int id = Convert.ToInt32(Products[i].id);
            string name = Products[i].Name;
            Get.Add(id, name);
        }
        return Get;
    }
    private void BindStaticLists()
    {
        Classes.CProducts cp = new Classes.CProducts();
        Products = cp.GetAll();
    }
    private void BindWarehouseDdl()
    {
        Dictionary<int, string> Items = new Dictionary<int, string>();
        List<Models.MwareHouse> get = new List<Models.MwareHouse>();
        Classes.CWareHouse cw = new Classes.CWareHouse();
        get = cw.GetAll();
        for (int i = 0; i < get.Count; i++)
        {
            string id = get[i].id;
            string name = get[i].Name;
            Items.Add(Convert.ToInt32(id), name);

        }
        ddlWareHouse.DataTextField = "Value";
        ddlWareHouse.DataValueField = "Key";
        ddlWareHouse.DataSource = Items;
        ddlWareHouse.DataBind();
    }
    #endregion

    protected void ddlProducts_SelectedIndexChanged(object sender, EventArgs e)
    {

    }

    protected void grdSales_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        GridViewRow gr = grdSales.SelectedRow;

    }

Solution

solved it

protected void ddlProducts_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList ddl = (DropDownList)sender;
        GridViewRow row = (GridViewRow)ddl.NamingContainer;
        TextBox txtName = (TextBox)row.FindControl("txtCp");
        txtName.Text = "*****";

    }